A variety of complex device are in widespread use today. Many of those devices have various operating parameters that indicate whether the device is functioning properly or if there may be a problem with the operation of the device. For example, fuel cell systems have specified threshold limits for certain performance variables. For example, there are temperature limits for various portions of a fuel cell system during acceptable operating conditions. There are also limits on output voltage or current for many fuel cell systems.
Significant study has been devoted to prognostics and health management (PHM) and principle component analysis (PCA) for detecting when a device is operating under conditions that depart from an expected or desired operating state. One limitation on such approaches is that the analysis is done with respect to the normal or baseline operation of the device instead of basing the analysis on threshold limits on the operating parameters.